• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권9호
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• pp.449-454
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• 2002

A rectangular straight microchannel, integrated with the resistance temperature detectors(RTDs) for temperature sensing and a micro-heater for generating the Temperature gradient along the channel, was fabricated. Its dimension is 57${\mu}{\textrm}{m}$(H)$\times$200${\mu}{\textrm}{m}$(W)$\times$48,050${\mu}{\textrm}{m}$(L), and RTDs were placed at the inner-channel wall. Si wafer was used as a substrate. For the fabrication of RTDs, 5300$\AA$ thick Pt/Ti layer was sputtered on a Pyrex glass wafer. Finally, the glass wafer was bonded with Si wafer by anodic bonding, so that the RTDs are located inside the microchannel. Temperature coefficient of resistance(TCR) values of the fabricated Pt-RTDs were 2800~2950ppm$^{\circ}C$ and the variation of TCR value In the range of O~10$0^{\circ}C$ was less than 0.3％. Therefore, it was proved that the fabricated Pt-RTDs without annealing were excellent as temperature sensors. The temperature distribution in the microchannel was investigated as a function of mass flow rate and heating power. The temperature increase rate diminished with decreasing the applied power and increasing the mass flow rate. It was confirmed from the comparison with the simulation results that the temperature measured inside the microchannel is more accurate than measuring the temperature measured at the outer wall. The proposed temperature sensing method and microchannel are expected to be useful in microfluidics researches.

• Restorative Dentistry and Endodontics
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• 제18권1호
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• pp.55-72
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• 1993

The aim of this study was to compare the marginal leakage of class II light curing composite resin restoration according to filling methods. With using acid etching technique and dentin bonding agent, various methods were suggested to eliminate or reduce the marginal leakage. In this study, class II cavities were prepared in 100 extracted human premolars with cementum margin(1mm below the CEJ) and the teeth were randomly assigned to 5 groups of 20 teeth each. The teeth in group 1, 2, 3 and 4 were restored by direct filling methods using P-50 and Clearfil Photoposterior of 10 teeth each, but the method of insertion of the restorative materials varied with each group. And the teeth in group 5 were restored by inlay method using Kulzer Inlay and CR Inlay. Filling methods are as follows : Group 1 : The composite resin was inserted in one layer in the proximal box and one layer in the occlusal portion. Group 2 : Insertion was in two equally thick horizontal layers in the proximal box. Group 3 : Insertion was in two diagonally placed layers in the proximal box. Group 4 : The composite resin was inserted in the same way as in group 3 except that a glass ionomer liner was first placed on the axial wall and gingival floor. Group 5 : The teeth were restored by Inlay technique using dure cure resin cement. All the teeth were thermocycled, stained with 1 % methylene blue solution, sectioned mesiodistally, and scored for marginal leakage. To compare the marginal leakage, ANOVA and T-test were used in analysis. The following results were obtained : 1. In direct filling methods, there was no significant difference in marginal leakage at both occlusal and cervical margins. 2. In all groups, occlusal margin showed significantly less leakage than cervical margin. 3. In group using glass ionomer liner, there was no significant reduction of marginal leakage at the cervical margin. 4. The group restored by inlay method showed significantly less marginal leakage than groups restored by direct filling methods at both occlusal and gingival margins. 5. There was no significant difference in each group according to filling materials.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.369-370
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• 2005

LTCC (Low Temperature Cofired Ceramic) technology is one of technologies which can realize SIP (System-In-a-Package). In this paper realization of gas sensor using LTCC technology was described. In the conventional gas sensor structure, wire bonding method is generally used as an interconnection method whereas in the LTCC sensor structure, via was used for the interconnection. As sensing materials, $SnO_2$ was adopted. The effect of frit glass portion on the adhesion of the sensing material to the LTCC substrate and the electrical conductivity of the sensing material were analyzed. AgPd, PdO, Pt was added to the sensing material as an additive for improving the gas sensitivity and electrical conductivity and the effect of the amount of additives in the sensing material on the electrical conductivity was investigated. The effect of the amount of frit glass in the termination on the sensor performance, especially mechanical integrity, was considered and the crack initiation and propagation in the boundary between the sensing material and the termination was studied.

• Restorative Dentistry and Endodontics
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• 제27권4호
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• pp.382-388
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• 2002

Compomer is composed of matrix and filler : matrix is made of the combination of resins and polycarboxylic molecules that are light-cured, and a filler is a glass component which is capable of ion-release. The resin content of compomers produces polymerization shrinkage which can adversely affect marginal adaptation. Pretreatment is a fundamental step which is treated with conditioner or primer in the use of these materials. Microleakage of restorative materials has been investigated mostly by dye penetration method. Dye penetration method was not quantitative and not measured repeatedly. Fluid filtration method, introduced and developed by Pashley's group, has been extensively used for 20 years for research purpose to understand the physiology of dentin, as well as the effects of various restorative treatments on dentin permeability. It permits quantitative, nondestructive measurment of microleakage in a longitudinal manner. The purpose of this study was to evaluate the change of dentin permeability according to the process of compomer restoration. In this study. Cl V cavities were prepared on buccal surface of thirty extracted human molars. The prepared cavities were etched by 37% phosphoric acid. The experimental teeth were randomly divided into three groups. Each group was treated with following materials Group 1 : Prime & Bond NT/Dyract AP, Group2： Single Bond/F2000 compomer, Group 3 : Syntac Single Component/Compoglass. The bonding agent and compomer were applied for each group following manufacturers information. Dentin permeability of each group was measured at each process by fluid filtration method; Step 1 : preparation(smear layer). Step 2 : etching(smear layer removal), Step 3 : applying the bonding agent, Step 4 : filling the compomer. Dentin permeability was expressed by hydraulic conductance ($\mu\textrm{l}$ min$^{-1}$cm$H_2O$$^{-1}$). The data were analysed statistically using One-way ANOVA and Sheffe's method. The results were as follows : 1. Dentin permeability differences between each process were significant except between step 1 and step 2(p<0.01). 2. Dentin permeability after removal of smear layer was highly increased(p<0.01). 3. In most case, decrease of dentin permeability was obtained by applying bonding agent(p<0.01). 4. Dentin permeability differences among the experimental groups were not significant(p>0.05). 5. None of compomers used in this study showed perfect seal at the interface.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.334-339
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• 2020

본 연구에서는 탄소섬유 및 유리섬유 강화 복합소재를 대상으로 하여, 접합면에 기계적인 결합력 향상을 위해 물리적인 표면처리 방법을 적용할 때, 알루미늄 및 복합소재, 복합소재 및 복합소재 간의 접합특성을 비교 분석하였다. 접합시편은 접합을 위해 쓰이는 모재 종류와 모재 접합면의 표면처리 방법으로 각각 구분하였다. 물리적인 표면처리 방법으로는 기계적인 마모 (사포) 처리, sand blasting 처리 및 플라즈마 처리기법을 적용하였다. 접합시편은 single lap joint 시편으로 제작하였으며 lap shear strength 측정 실험을 진행하여 그 결과값을 비교하였다. 실험 결과에서 기계적인 마모 및 sand blasting 표면 처리 방법이 물리적인 표면 처리를 진행하지 않은 일반 시편 대비하여 약 4~5배의 접합강도 향상이 있음을 확인하였다. 플라즈마 처리 기법을 적용한 방안에서는 플라즈마 출력과 처리 시간을 150 W 5분, 150 W 10분 및 300 W 3분 처리 조건으로 정의하여 실험을 진행하였으며, lap shear strength 결과에서 앞선 기계적 표면 처리 방안과 유사한 결과를 보였다. 다만 처리 조건에 따라서 접합특성에 미치는 영향은 적음을 확인하였다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.129-133
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• 2001

In this paper, hermetic sealing was studied fur wafer level packaging of the MEMS devices. With the flip-chip bonding method, this B-stage epoxy sealing will be profit to MEMS device sealing and further more RF-MEMS device sealing. B-stage epoxy can be cured 2-step and hermetic sealing can be obtained. After defining $500{\mu}{\textrm}{m}$-width seal-lines on the glass cap substrate by screen printing, it was pre-baked at $90^{\circ}C$ for about 30 minutes. It was then aligned and bonded with device substrate followed by post-baked at $175^{\circ}C$ for about 30 minutes. By using this 2-step baking characteristic, the width and the height of the seal-line were maintained during the sealing process. The height of the seal-line was controlled within $\pm0.6${\mu}{\textrm}{m}$ and the strength was measured to about 20MPa by pull test. The leak rate of the epoxy was about $10^7$ cc/sec from the leak test.

• 한국건축시공학회지
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• 제1권1호
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• pp.143-150
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• 2001

Permanent-Form is one of system forms for reducing human labor, work costs, oscillation, noise, construction wastes and so on. Permanent-Form is made from precast method in facilities, and carried in construction site to assemble with no demolding. The biggest expense to produce permanent-Form is about manufacturing mold. This papers about structural efficiency evaluation, construction efficiency test. The result of this study is below. (1) In the compressive strength test of column. Fly ash specimen and polymer specimen's strength developed as each 8%, 14% to comparison with standard specimen. The reason of this result from form section area increase and form's reinforcing bar (2) The Degree of column crack in permanent form is lower than another one's The glass fiber's fiber reinforcement effect brings like this. (3) In the flexural load test of beam, the early crack load and maximum load of permanent form use specimen showed 20% higher than standard specimen's. (4) In field application experiment, an constructional error is satisfied with the allowable margin of error, $\pm$5mm (5) When the concrete is placed into the form inside, The transformation degree of permanent form is lower than plywood form's. (6) The concrete packing ability of permanent form is satisfactory. (7) The bonding strength of permanent form shows enough strength - 6kgf/$\textrm{cm}^2$.

• 한국정밀공학회지
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• 제21권2호
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• pp.195-202
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• 2004

This paper presents the fabrication and evaluation of mechanical behavior for a peristaltic micropump by flow simulation. The valve-less micropump using the diffuser/nozzle is consists of the lower plate, the middle plate, the upper plate and the tube that connects inlet and outlet of the pump. The lower plate includes the channel and the chamber, and the plain middle plate are made of glass and actuated by the piezoelectric translator. Channels and a chamber on the lower plate are fabricated on high processability silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The upper plate does the roll of a pump cover and has inlet/outlet/electric holes. Three plates are laminated by the aligner and bonded by the anodic bonding process. Flow simulation is performed using error-reduced finite volume method (FVM). As results of the flow simulation and experiments, the single chamber pump has severe flow problems, such as a backflow and large fluctuation of a flow rate. It is proved that the double-chamber micropump proposed in this paper can reduce the drawback of the single-chamber one.

• 한국염색가공학회지
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• 제27권2호
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• pp.126-131
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• 2015

Silica-polyurethane hybrid breathable films were prepared and their breathabilities were assessed. Appropriately aggregated silica was prepared through sol-gel reaction of water glass and its particle size ranged 360~500nm. The polyurethane dispersion was prepared by the reaction of isophorone diisocyanate(IPDI) as diisocyanate and polytetramethylene glycol(PTMG) and dimethylol propionic acid(DMPA) as polyol, particle size ranging 30~120nm. The reaction between isocyanate and hydroxyl group to form urethane bonding was checked by the intensity of the stretch peak of isocyanate at $2270cm^{-1}$ in the FT-IR. The silica was incorporated into polyurethane dispersion and casted into film. It was shown that the incorporated silica(1~5wt.%) increased water vapour permeability of the films by 30~100%, and decreased the hydrostatic pressure by 10~40%. From the results, it could be concluded that the appropriate hybridization of silica can increase the breathability of polyurethane dispersion film, while minimizing the loss of hydrostatic pressure.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.448-456
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• 2010

The mechanical behavior of granular soils is affected by particle bonding including natural cementation. This study addresses a simple model of small strain stiffness and salt concentration based on wave measurements of salt-cemented particulate media. Published models of artificially cemented soils with different curing methods and several types of cementation agents are reviewed. Glass beads with the median diameter of D50 = 0.5mm are prepared in rectangular cells using the water-pluviated method in salt water with different concentrations. Piezo disk elements and bender elements embedded in the cell are used for the measurements of compressional and shear waves. The relationships between elastic wave velocities and salt concentration show an exponential function. The measured small strain stiffness matches well the predicted small strain stiffness based on micromechanics for simple cubic monosized sphere particles. This study demonstrates that the salt concentration in salt-cemented specimen may be evaluated by using elastic wave velocities.